Air staged catalytic combusion system

ABSTRACT

A system and method of combusting a hydrocarbon fuel is disclosed. The system and method combines the accuracy and controllability of an air staging system with the ultra-low emissions achieved by catalytic combustion systems. The present invention can achieve ultra-low emissions while maintaining the combustion system pressure drop constant over a wide range of power levels, with essentially no consequent impact on engine efficiency. Also, the present technology is easily applied to a multitude of different systems, such as conventional lean operating catalysts. One aspect of the invention is a system for combusting hydrocarbon fuel, which includes an air supply for supplying air from a compressor to the air inlet, an air inlet for entrance of an air mixture from the compressor, at least one air staging valve that directs air to a catalyst module and a bypass manifold. The catalyst module receives fuel and air, which mixes with a catalyst contained therein. The catalyst partially oxidizes the fuel to generate a heat of reaction and a partial oxidation product stream comprising hydrogen and carbon oxides. The fuel and air from the catalyst module is then delivered to a main combustor that is capable of completely combusting the partial oxidation product stream to generate an effluent gas stream. The system may also contain at least one preheater combustor, which is upstream from the catalyst module and downstream from the air staging valve. The result is a system and method that offers ultra-low emissions over a wide range of power levels, fuel properties and ambient operating conditions.

BACKGROUND OF THE INVENTION

[0001] The present invention generally relates to a method and systemfor combusting hydrocarbon fuels with resulting ultra-low emissions,over a wide range of power levels, fuel properties and ambient operatingconditions.

[0002] The conventional gas turbine combustor, as used in a gas turbinepower generating system, requires a mixture of fuel and air which isignited and combusted uniformly. Generally, the fuel injected from afuel nozzle into the inner tube of the combustor is mixed with air forcombustion, fed under pressure from the air duct, ignited by a sparkplug and combusted. The gas that results is lowered to a predeterminedturbine inlet temperature by the addition of cooling air and dilutentair, then injected through a turbine nozzle into a gas turbine.

[0003] It is well known within the art that exhaust gases produced bycombusting hydrocarbon fuels can contribute to atmospheric pollution.This occurrence is attributed to the development of localized hightemperature zone, which can exceed 2,000° C. Exhaust gases typicallycontain many undesirable pollutants such as nitric oxide (NO) andnitrogen dioxide (NO₂), which are frequently grouped together asNitrogen Oxides (NO_(x)), unburned hydrocarbons (UHC), carbon monoxide(CO), and particulates, primarily carbon soot.

[0004] Several methods are known in the art to decrease NO_(x)emissions. For example, the formation of fuel-bound NO_(x) can beminimized or avoided entirely by burning a low nitrogen or nitrogen-freefuel. However, burning a low nitrogen fuel does nothing to reduce theformation of thermal or prompt NO_(x). The formation of thermal NO_(x)can be reduced by operating under uniformly fuel-lean conditions, suchas by using a lean diffusion flame or a lean premixed/prevaporized (LPP)system. The excess air used to achieve fuel-lean combustion acts as adiluent to lower flame temperatures, thereby reducing the amount ofthermal NO_(x) formed. Prompt NO_(x) can also be reduced by operatingunder fuel-lean conditions. However, the extent to which thermal andprompt NO_(x) formation can be reduced by fuel-lean combustion may belimited by flame instability that occurs at very lean conditions.

[0005] By way of example, Honeywell Air Staged Combustion Systems asused in the ASE120 and ASE50DLE industrial engines are air-staged lean,premixing (LP) combustion systems. Air from the compressor flows overthe combustor wall to provide convective cooling and then to at leastone three-way air staging valve. Depending on their position, thesevalves direct air either to the premixers, where the fuel is added andmixed prior to burning in the combustor, or to a bypass manifold whichinjects the air downstream of the flame just upstream of the turbine. Bymodulating the air staging valves the flame temperature can be heldsubstantially constant from no-load to peak conditions. An advantage ofthis system is that all of the compressed air is routed through theturbine, and there is no loss of efficiency as in bleed-type air stagingsystems. At no-load conditions, a large amount of air is bypassed,allowing the flame temperature to be held close to the ideal for lowemissions. This provides a system that is accurate and controllable overa wide range of power levels, fuel properties and ambient operatingconditions. However, it is not capable of achieving ultra-low emissions.

[0006] Catalytic combustion systems, though, are capable of achievingultra-low emissions. Catalytic combustion systems using a solid phasecatalyst are known within the art. However, catalytic combustion systemsare not able to offer the accuracy and controllability of the airstaging system over a wide range of power levels, fuel properties andambient operating conditions. Present systems are not capable ofmaintaining the pressure drop constant with essentially no consequentimpact on engine efficiency. Further, present technology is not easilyapplied to a multitude of different systems, such as conventional leanoperating catalysts.

[0007] Accordingly, what is needed in the art is a method and system forcombusting hydrocarbon fuels that is accurate, controllable, easilyadapted to a wide range of power levels, fuel properties and ambientoperating conditions and offers ultra-low emissions.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to a method and system forcombusting hydrocarbon fuels over a wide range of power levels, fuelproperties and ambient operating conditions that results in ultra-lowemissions. The present technology is capable of maintaining the pressuredrop constant with essentially no consequent impact on engineefficiency, and is easily applied to a multitude of different systems,such as conventional lean operating catalysts.

[0009] One aspect of the invention is a system for combustinghydrocarbon fuel, which includes an air supply for supplying air from acompressor to the air inlet, an air inlet for entrance of an air mixturefrom the compressor, at least one air staging valve that directs air toa catalyst module and a bypass manifold. The catalyst module receivesfuel and air, which contacts a catalyst that is contained within thecatalyst module. The catalyst partially oxidizes the fuel to generate aheat of reaction and a partial oxidation product stream comprisinghydrogen and carbon oxides. The fuel and air from the catalyst module isthen delivered to a main combustor that is capable of completelycombusting the partial oxidation product stream to generate an effluentgas stream. The system may also contain at least one preheater combustorwhich is upstream from the catalyst module and down stream from the airstaging valve.

[0010] In another aspect of the present invention, a method ofcombusting a hydrocarbon fuel is disclosed. Air is compressed, forced toflow over the combustor walls to provide convective cooling, thendivided into at least one air staging valve air stream and at least onesecondary air stream. The air staging valve air stream is controllablydivided into at least one bypass flow stream, and at least one maincombustion air stream. According to an embodiment, the air iscontrollably divided through the use of an air staging valve. Theposition of the air staging valve dictates which direction the air willflow. The bypass flow stream may be injected with a secondary airstream, to form an exit profile control air stream that is just upstreamof the turbine. In this way, the pressure drop of the system is keptessentially constant with no consequent impact on engine efficiency. Thebypass flow stream and secondary air stream may also be directlyinjected to the combustor. The secondary air stream may be used to setthe exit effluent gas stream temperature. It is envisioned that thesecondary air stream, bypass flow stream, and exit profile streams maybe configured in a multitude of different configurations as desired.This may include combining the secondary air stream and bypass flowstream prior to introduction to the combustor. Also, the secondary airstream and bypass flow stream may be directly introduced to the maincombustor or exit to the turbine. The main combustion air stream isintroduced into a fuel preparation section, wherein main fuel isinjected and mixed to form a pre-catalyst mixture. The pre-catalystmixture is introduced into a catalyst section, wherein a catalyst islocated, and partially oxidizes the fuel by contacting the catalystmixture with an oxidation catalyst in a catalytic oxidation stage. Thisgenerates a heat of reaction and a partial oxidation product streamcomprising hydrocarbons and carbon monoxide. The partial oxidationproduct stream is then combusted in a main combustor, at a condition atwhich appreciable quantities of thermal NO_(x) are not formed. Thetemperature and composition of the partial oxidation product stream areselected to control simultaneously the amounts of NO_(x) formed in themain combustor and the stability of the flame in the main combustor,thereby controlling the total amount of NO_(x) in the exit effluent gasstream. Typically this will result in ultra-low emissions on the orderof less than 5 ppm. The exit effluent gas stream may be created bycombining the effluent gas stream generated by the flame and the exitprofile control air stream. This exit effluent gas stream may then bedelivered to a combustor or turbine.

[0011] According to another embodiment, preheaters are utilized in orderto start the engine, vaporize liquid fuel and to raise the temperatureof the incoming gases to the catalyst activation temperature at lowpower settings. The compressor outlet temperature is typically highenough to activate the catalysts at high power settings. Therefore, thepreheaters are only necessary for operation at low power, eliminatingpreheater emissions at higher power settings. For engines in which thecompressor outlet temperature is insufficient to activate the catalystat even high power, the preheaters may be run at high power but thepreheater NO_(x) emissions will then contribute to the total exhaustNO_(x) emissions and the preheater combustor design may then be of thelow (less than 10 ppm), as opposed to ultra-low (less than 5 ppm),NO_(x) type. The fuel injectors and preheaters may be designed foreither or both liquid and gaseous fuels. Only a small fraction of thecompressor air is fed to the preheaters, the remaining air will be mixedwith the preheated air prior to introduction of the main fuel.

[0012] According to an embodiment, a method of combusting hydrocarbonfuel is disclosed, comprising compressing an air stream in a compressor,dividing the air stream into a first air staging valve air stream, asecond air staging valve air stream and one secondary air stream. Airstaging valves are utilized to controllably divide said first airstaging valve air stream into a first bypass flow stream and a firstpreheater air stream. The second air staging valve air stream iscontrollably divided into a second bypass flow stream and a secondpreheater air stream. A portion of the first preheater air stream isdivided to form a first main combustion air stream and a portion of thesecond preheater air stream is divided to form a second main combustionair stream. Preheater fuel is mixed with the first preheater air streamto form a first fuel/air mixture and preheater fuel is mixed with thesecond preheater air stream to form a second fuel/air mixture. The firstfuel/air mixture is combusted in a first preheater combustor andcreating a first fuel/air product stream. The second fuel/air mixture iscombusted in a second preheater combustor, creating a second fuel/airproduct stream. The first fuel/air product stream is combined with thefirst main combustor air stream and the resultant mixture is introducedinto a first fuel preparation section, wherein main fuel is injected andmixed to form a first pre-catalyst mixture. The second fuel/air productstream is combined with second main combustor air stream and theresultant mixture is introduced into a second fuel preparation section,wherein main fuel is injected and mixed to form a second pre-catalystmixture. The first pre-catalyst mixture is introduced into a firstcatalyst section, wherein a catalyst is located and partially oxidizesthe fuel by contacting the first pre-catalyst mixture with an oxidationcatalyst in a catalytic oxidation stage, thereby generating a heat ofreaction and a first partial oxidation product stream comprisinghydrocarbons and carbon monoxide. The second pre-catalyst mixture isintroduced into a second catalyst section, wherein a catalyst is locatedand partially oxidizes the fuel by contacting the second pre-catalystmixture with an oxidation catalyst in a catalytic oxidation stage,thereby generating a heat of reaction and a second partial oxidationproduct stream comprising hydrocarbons and carbon monoxide. The firstpartial oxidation product stream may be combusted in a first maincombustor, at a condition at which appreciable quantities of thermalNO_(x) are not formed, thereby generating a first effluent gas stream.The second partial oxidation product stream may be combusted in a secondmain combustor, at a condition at which appreciable quantities ofthermal NO_(x) are not formed, thereby generating a second effluent gasstream. Also, the first and second main combustors may be combined toform a single combustor. The first effluent gas stream may be combinedwith the second effluent gas stream, first exit profile control airstream, and second exit profile control air stream to form an exiteffluent gas stream. The temperature and composition of said firstpartial oxidation product stream and said second partial oxidationstream are selected to control simultaneously the amounts of NO_(x)formed in the main combustor and the stability of the flame in saidfirst main combustor and said second main combustor, thereby controllingthe total amount of NO_(x) in the exit effluent gas stream.

[0013] These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdrawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a cross-sectional view of a prior art staged combustionsystem;

[0015]FIG. 2 is a schematic of air-staged catalytic combustion systemaccording to the present invention;

[0016]FIG. 3 is a schematic of the air staged catalytic combustionsystem according to the present invention; and

[0017]FIG. 4 is a cross-sectional view of the integration of catalystinto a combustion system.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention generally relates to a method and systemfor combusting hydrocarbon fuels with resulting ultra-low emissions,over a wide range of power levels, fuel properties and ambient operatingconditions.

[0019]FIG. 1 depicts a cross-sectional view of an air stage combustionsystem as known in the art. Air from a compressor enters entrance 10flows over the walls of combustor 18, to provide convective cooling,then to one or more three-way air staging valves 12. Depending on theirposition, the air staging valves 12 direct air, via a combustion airmanifold 16, to either premixers, not shown, where the fuel is added andmixed prior to burning in the combustor 18, or to a bypass manifold 14which injects the air downstream of the flame just upstream of theturbine. By modulating the air staging valves 12 the flame temperaturecan be held substantially constant from no-load to peak load conditions.An advantage of this system is that all of the compressed air is routedthrough the turbine, not shown, and there is no loss of engineefficiency as in bleed-type air-staging systems. At no-load conditions,a large amount of air is bypassed, allowing the flame temperature to beheld close to the ideal for low emissions. As the fuel flow increasesfor higher power settings, the amount of combustion air in theCombustion Air Manifold 16 is increased, keeping the flame temperatureconstant. Fuel, either liquid or gaseous, is injected into theCombustion Air Manifold 16 and mixed in the premixers. Premixed gasesare injected into the combustor 18 through the premixer exits 24. Theflame is stabilized in a downstream Combustion Chamber 18. Dilution air21 is introduced into the Combustion Chamber 18 downstream of the flameto control the exit temperature profile at the turbine nozzle 22. Oncethe combustion process is complete, effusion wall cooling 20 isintroduced in the dilution section. In its lean, premixed form, theflame temperature is controlled to around 1800 K (2780° F.) by varyingthe position of the air staging valves 12. A closed loop control is usedto position the air staging valves 12, the source of the signal to drivethe control system may be an air pressure drop, a flame sensor ordirectly measured emissions. The combination of an active control systemwith air staging offers the advantage that the flame temperature ismaintained at any desired value at all operating conditions. The twopremixers may be individually tuned to compensate for small flowdiscrepancies in either the air or fuel systems. The effluent gas streamcreated is delivered to the turbine through the turbine nozzle 22. Thissystem allows for a wide range of operating and ambient conditions,providing accuracy and controllability. However, prior art air stagingsystems do not have the capability of achieving ultra-low emissions. Itis a purpose of the present invention to incorporate many of thepositive attributes of an air staged combustion system with the positiveattributes of a catalytic system. The combination of the accuracy andcontrollability of an air staging system with the ability to achieveultra-low emissions represents a significant advance in the art.

[0020] One aspect of the invention may be a system for combustinghydrocarbon fuel, which includes an air supply for supplying air from acompressor to the air inlet, an air inlet for entrance of an air mixturefrom the compressor, at least one air staging valve that directs air toa catalyst module and a bypass manifold. The catalyst module may receivefuel and air, which contacts a catalyst contained therein. The catalystpartially oxides the fuel to generate a heat of reaction and a partialoxidation product stream comprising hydrocarbons and carbon oxides. Thefuel and air from the catalyst module may then be delivered to a maincombustor that is capable of completely combusting the partial oxidationproduct stream to generate an effluent gas stream. The system may alsocontain at least one preheater combustor which is upstream from thecatalyst module and down stream from the air staging valve.

[0021] In one aspect of the present invention, a method of combusting ahydrocarbon fuel is disclosed. Air may be compressed, forced to flowover the compressor walls to provide convective cooling, then dividedinto at least one air staging valve air stream and at least onesecondary air stream. The air staging valve air stream may becontrollably divided into at least one bypass flow stream, and at leastone main combustion air stream. According to a one embodiment the airmay be controllably divided through the use of an air staging valve. Theposition of the air staging valve dictates which direction the air willflow. The bypass flow stream may inject the air with a secondary airstream to form an exit profile control air stream that is just upstreamof the turbine. In this way, the pressure drop of the system may be keptessentially constant with no consequent impact on engine efficiency. Themain combustion air stream may be introduced into a fuel preparationsection, wherein main fuel is injected and mixed to form a catalystmixture. The catalyst mixture may be introduced into a catalyst section,wherein a catalyst may be located and partially oxidizes the fuel bycontacting the catalyst mixture with an oxidation catalyst in acatalytic oxidation stage. This generates a heat of reaction and apartial oxidation product stream comprising hydrocarbons and carbonmonoxide. The partial oxidation product stream may then be combusted ina main combustor, at a condition at which appreciable quantities ofthermal NO_(x) are not formed. The temperature and composition of thepartial oxidation product stream may be selected to controlsimultaneously the amounts of NO_(x) formed in the main combustor andthe stability of the flame in the main combustor, thereby controllingthe total amount of NO_(x) in the exit effluent gas stream. Typicallythis will result in ultra-low emissions on the order of less than 5 ppm.The effluent gas stream may be created by combining the effluent gasstream generated and the exit profile control air stream. This effluentgas stream may then be delivered to a turbine.

[0022] According to another embodiment, preheaters may be utilized inorder to start the engine, vaporize liquid fuel and to raise thetemperature of the incoming gases to the catalyst activation temperatureat low power settings. The compressor outlet temperature is typicallyhigh enough to activate the catalysts at high power settings. Therefore,the preheaters may only be necessary for operation at low power,eliminating preheater emissions at higher power settings. For engines inwhich the compressor outlet temperature is insufficient to activate thecatalyst at even high power, the preheaters may be run at high power butthe preheater NO_(x) emissions will then contribute to the total exhaustNO_(x) emissions and the preheater combustor design could then be of thelow (less than 10 ppm), as opposed to ultra-low (less than 5 ppm),NO_(x) type. The fuel injectors and preheaters may be designed foreither or both liquid and gaseous fuels. Only a small fraction of thecompressor air may be fed to the preheaters, the remaining air may bemixed with the preheated air prior to introduction of the main fuel.

[0023]FIG. 2 is a schematic depicting an embodiment of the presentinvention utilizing a preheater. As shown, air may be compressed in acompressor, resulting in an incoming air stream 25. The incoming airstream 25 may be divided into at least one air staging valve air stream26 and at least one secondary air stream 28. According to an embodimentthe air staging valve air stream 26 may be controllably divided, by anair staging valve 30, into one bypass flow stream 27 and one preheaterair stream 32. The bypass flow stream 27 and secondary air stream 28 maybe combined to form an exit profile control air stream 34.Alternatively, the bypass flow stream may be injected separately intothe main combustor 54. A portion of the preheater air stream 32 isdivided to form a main combustion air stream 36. Preheater fuel 38 maybe added to the preheater air stream 32 to form a fuel/air mixture, thefuel/air mixture is combusted in a preheater combustor 40 and results ina fuel/air product stream 42. The fuel/air product stream 42 is mixedwith the main combustor air stream 36 and the resultant mixture isintroduced into a fuel preparation section 44, wherein main fuel 46 isinjected and mixed to form a pre-catalyst mixture 48. The pre-catalystmixture 48 is then introduced into a catalyst section 50, wherein acatalyst is located and partially oxidizes the fuel by contacting thecatalyst mixture with an oxidation catalyst in a catalytic oxidationstage. The catalyst may be any catalyst known within the art. By way ofexample, the catalyst may be platinum, rhodium, iridium, ruthenium,palladium, chromium oxides, cobalt oxides, alumina and mixtures thereof.This process generates a heat of reaction and a partial oxidationproduct stream 52 comprising hydrocarbons and carbon monoxide. Thetemperature and composition of the partial oxidation product stream 52are selected to control simultaneously the amounts of NO_(x) formed inthe main combustor 54 and the stability of the flame in the maincombustor 54, thereby controlling the total amount of NO_(x) in the exiteffluent gas stream 60.

[0024]FIG. 3 is a schematic depicting an embodiment of an air stagedcatalytic combustion system according to the present invention. Air in62 from compressor, not shown, is divided into three air streams. Thereare two air staging valve air streams 64, and a secondary air stream 66.The air staging valve air streams 64, are controllably divided by an airstaging valve 68, which controls the air in such a manner that thepressure drop of the system is kept essentially constant with noconsequent impact on engine efficiency. For example, as the air passageto the preheater/catalyst section 70 is reduced the bypass flow stream72 is opened. This allows for added control. The air that is deliveredto the preheater/catalyst section 70, is partially oxidized thendelivered to the combustor 71. The preheater is optional and notrequired. The compressor outlet temperature is typically high enough toactivate the catalysts at high power setting. Therefore, the preheatermay be used for many reasons such as to raise the temperature of theincoming gases to the catalyst activation temperature at low powersettings. Also, it may be desirable for a number of other reasonsincluding to start the engine and liquid fuel vaporization. Within thecombustor 71 the velocity may be reduced and a lean-premixed flame canstabilize. The catalyst system can stabilize a very lean flame byproviding preheat and reactive species. This gives sufficient reactivityto burn out hydrocarbons and carbon monoxide at flame temperatures lessthan 1700 K, considerably less than that of conventional lean premixedflames. The effluent gas stream 76 is then combined with the exitprofile control air stream 78 to form an exit effluent gas stream 80.The bypass flow stream 72, travels through a bypass manifold 74. Theexit profile control air stream 78 is formed by combining the secondaryair stream 66 with the bypass flow stream 72. It is then combined withthe effluent gas stream 76 and secondary air stream 66 to form the exiteffluent gas stream 80 to turbine. Alternatively the secondary airstream 66 and the bypass air stream 72 may be combined separately withthe effluent gas stream 76 to form the exit effluent gas stream 80.

[0025]FIG. 4 is a cross-sectional view depicting, according to anembodiment, the integration of the catalyst section into the system. Asshown, a fraction of air from air staging valves 82 is led over thepreheater combustor 86 walls and into the preheater to become preheaterair 90. The preheating of main air and fuel occurs in the fuelpreparation section 92 as in mixes with the hot, burned products of thepreheater combustion. Within the preheater combustor area 86 preheaterfuel 88 is added. The mixture is combusted and proceeds to the fuelpreparation section 92, wherein main fuel 94 is added along with airfrom the air staging valves 82 and the preheater air 90, the resultingmixture formed is a pre-catalyst mixture 96. It should be noted that thepre-catalyst mixture 96 refers to the mixture prior to its addition tothe catalyst section 98. The pre-catalyst mixture 96 is then introducedto the catalyst section 98, wherein at least one catalyst is located,and a partial oxidation stream 100 results. The partial oxidation stream100, is then led to the main combustor 102. Because a partial oxidationreaction takes place within the catalyst module it is necessary tomaintain a high enough gas velocity in the area where the catalystexits, known as the catalyst exit duct 104, to prevent flashback flameinto the catalyst exit duct 104. Also, the catalyst exit duct 104 shouldbe sized to eliminate the risk of auto-ignition at high pressureespecially on liquid fuels.

[0026] It should be understood, of course, that the foregoing relates topreferred embodiments of the invention and that modifications may bemade without departing from the spirit and scope of the invention as setforth in the following claims.

We claim:
 1. A method of combusting hydrocarbon fuel, comprising:compressing an air stream in a compressor; dividing the air stream intoat least one air staging valve air stream and at least one secondary airstream; controllably dividing said air staging valve air stream into atleast one bypass flow stream, and at least one main combustion airstream; introducing said main combustion air stream into a fuelpreparation section, wherein main fuel is injected and mixed to form apre-catalyst mixture; introducing said pre-catalyst mixture into acatalyst section, wherein a catalyst is introduced and partiallyoxidizes the fuel by contacting said pre-catalyst mixture with anoxidation catalyst in a catalytic oxidation stage, thereby generating aheat of reaction and a partial oxidation product stream comprisinghydrocarbons and carbon monoxide; combusting said partial oxidationproduct stream, in a main combustor, at a condition at which appreciablequantities of thermal NO_(x) are not formed, thereby generating aneffluent gas stream; introducing said effluent gas stream to at leastone combustor; introducing said secondary air stream to at least onecombustor; introducing said bypass flow stream to at least onecombustor; and wherein the temperature and composition of said partialoxidation product stream are selected to control simultaneously theamounts of NO_(x) formed in said main combustor and the stability of theflame in said main combustor, thereby controlling the total amount ofNO_(x) in said exit effluent gas stream.
 2. A method as in claim 1,further comprising the steps of: combining said bypass flow stream andsaid secondary air stream to form an exit profile control air stream;and introducing said exit profile control air stream to at least onecombustor.
 3. A method as in claim 2, further comprising the steps ofcombining said effluent gas stream with said exit profile control airstream to form an exit effluent gas stream; and introducing said exiteffluent gas stream to at least one combustor.
 4. A method as in claim1, further comprising the step of introducing said secondary air streamto said main combustor.
 5. A method as in claim 1, further comprisingthe step of introducing said bypass flow stream to said main combustor.6. A method as in claim 1, further comprising a valve for controllablydividing said air staging valve air stream.
 7. A method as in claim 1,wherein the temperature and composition of the partial oxidation productstream are selected to control simultaneously the amount of thermalNO_(x) and prompt NO_(x) formed in the main combustor.
 8. A method as inclaim 1, wherein said catalyst is selected from the group consisting ofplatinum, rhodium, iridium, ruthenium, palladium, chromium oxides,cobalt oxides, alumina and mixtures thereof.
 9. A method as in claim 1,wherein said fuel is in liquid form.
 10. A method as in claim 1, whereinsaid fuel is in gaseous form.
 11. A method as in claim 3, furthercomprising the step of delivering said exit effluent gas stream to aturbine.
 12. A method of combusting hydrocarbon fuel, comprising:compressing an air stream in a compressor; dividing the air stream intoat least one air staging valve air stream and at least one secondary airstream; controllably dividing said air staging valve air stream into atleast one bypass flow stream, and at least one preheater air stream;allowing a portion of said preheater air stream to be divided to form amain combustion air stream; mixing preheater fuel with said preheaterair stream to form a fuel/air mixture; combusting said fuel/air mixturein a preheater combustor and creating a fuel/air product stream; mixingsaid fuel/air product stream with said main combustor air stream andintroducing the resultant mixture into a fuel preparation section,wherein main fuel is injected and mixed to form a pre-catalyst mixture;introducing said pre-catalyst mixture into a catalyst section, wherein acatalyst is located and partially oxidizes the fuel by contacting saidpre-catalyst mixture with an oxidation catalyst in a catalytic oxidationstage, thereby generating a heat of reaction and a partial oxidationproduct stream comprising hydrocarbons and carbon monoxide; combustingsaid partial oxidation product stream, in said main combustor, at acondition at which appreciable quantities of thermal NO_(x) are notformed, thereby generating an effluent gas stream; and wherein thetemperature and composition of said partial oxidation product stream areselected to control simultaneously the amounts of NO_(x) formed in saidmain combustor and the stability of the flame in said main combustor,thereby controlling the total amount of NO_(x) emissions.
 13. A methodas in claim 12, further comprising the steps of: combining said bypassflow stream and said secondary air stream to form an exit profilecontrol air stream; and introducing said exit profile control air streamto at least one combustor.
 14. A method as in claim 13, furthercomprising the steps of: combining said effluent gas stream with saidexit profile control air stream to form an exit effluent gas stream; andintroducing said exit effluent gas stream to at least one combustor. 15.A method as in claim 12, further comprising the step of introducing saidsecondary air stream to said main combustor.
 16. A method as in claim12, further comprising the step of introducing said bypass flow streamto said main combustor.
 17. A method as in claim 12, further comprisinga valve for controllably dividing said air staging valve air stream. 18.A method as in claim 12, wherein the temperature and composition of saidpartial oxidation product stream are selected to control simultaneouslythe amount of thermal NO_(x) and prompt NO_(x) formed in said maincombustor.
 19. A method as in claim 12, wherein said catalyst isselected from the group consisting of platinum, rhodium, iridium,ruthenium, palladium, chromium oxides, cobalt oxides, alumina andmixtures thereof.
 20. A method as in claim 12, wherein said fuel is inliquid form.
 21. A method as in claim 12, wherein said fuel is ingaseous form.
 22. A method as in claim 12, further comprising the stepof vaporizing a liquid fuel within said preheater.
 23. A method as inclaim 12, further comprising the step of delivering said exit effluentgas stream to a turbine.
 24. A method of combusting hydrocarbon fuel,comprising: compressing an air stream in a compressor; dividing the airstream into a first air staging valve air stream, a second air stagingvalve air stream and one secondary air stream; utilizing an air stagingvalve to controllably divide said first air staging valve air streaminto a first bypass flow stream and a first preheater air stream;utilizing an air staging valve to controllably divide said second airstaging valve air stream into a second bypass flow stream and a secondpreheater air stream; allowing a portion of said first preheater airstream to be divided to form a first main combustion air stream;allowing a portion of said second preheater air stream to be divided toform a second main combustion air stream; mixing preheater fuel withsaid first preheater air stream to form a first fuel/air mixture; mixingpreheater fuel with said second preheater air stream to form a secondfuel/air mixture; combusting said first fuel/air mixture in a firstpreheater combustor and creating a first fuel/air product stream;combusting said second fuel/air mixture in a second preheater combustorand creating a second fuel/air product stream; mixing said firstfuel/air product stream with said first main combustor air stream andintroducing the resultant mixture into a first fuel preparation section,wherein main fuel is injected and mixed to form a first pre-catalystmixture; mixing said second fuel/air product stream with said secondmain combustor air stream and introducing the resultant mixture into asecond fuel preparation section, wherein main fuel is injected and mixedto form a second pre-catalyst mixture; introducing said firstpre-catalyst mixture into a first catalyst section, wherein a catalystis introduced and partially oxidizes the fuel by contacting said firstpre-catalyst mixture with an oxidation catalyst in a catalytic oxidationstage, thereby generating a heat of reaction and a first partialoxidation product stream comprising hydrocarbons and carbon monoxide;introducing said second pre-catalyst mixture into a second catalystsection, wherein a catalyst is introduced and partially oxidizes thefuel by contacting said second pre-catalyst mixture with an oxidationcatalyst in a catalytic oxidation stage, thereby generating a heat ofreaction and a second partial oxidation product stream comprisinghydrocarbons and carbon monoxide; combusting said first partialoxidation product stream, in a first main combustor, at a condition atwhich appreciable quantities of thermal NO_(x) are not formed, therebygenerating a first effluent gas stream; combusting said second partialoxidation product stream, in a second main combustor, at a condition atwhich appreciable quantities of thermal NO_(x) are not formed, therebygenerating a second effluent gas stream; combining said first effluentgas stream, said second effluent gas stream, said first exit profilecontrol air stream, and said second exit profile control air stream toform an exit effluent gas stream, wherein the temperature andcomposition of said first partial oxidation product stream and saidsecond partial oxidation stream are selected to control simultaneouslythe amounts of NO_(x) formed in the main combustor and the stability ofthe flame in said first main combustor and said second combustor,thereby controlling the total amount of NO_(x) in the exit effluent gasstream.
 25. A method as in claim 24, wherein the temperature andcomposition of the partial oxidation product stream are selected tocontrol simultaneously the amount of thermal NO_(x) and prompt NO_(x)formed in said main combustor
 26. A method as in claim 24, wherein saidcatalyst is selected from the group consisting of platinum, rhodium,iridium, ruthenium, palladium, chromium oxides, cobalt oxides, aluminaand mixtures thereof.
 27. A method as in claim 24, wherein said fuel isin liquid form.
 28. A method as in claim 24, wherein said fuel is ingaseous form.
 29. A method as in claim 24, further comprising the stepof vaporizing a liquid fuel within the fuel preparation section.
 30. Amethod as in claim 24, further comprising the step of delivering saidexit effluent gas stream to a turbine.
 31. A system for combustinghydrocarbon fuel, comprising: an air supply for supplying air from acompressor to the air inlet; an air inlet for entrance of said airmixture from said compressor; at least one air staging valve, whereinsaid air staging valve directs air to a catalyst module and a bypassmanifold; at least one a bypass manifold for receiving said air directedfrom said air staging valve; at least one catalyst module for receivingsaid fuel and air directed from said air staging valve; at least onecatalyst exit duct for delivering said fuel and air from said catalystmodule to a main combustor; and an exit for delivering the effluent gasstream generated by the main combustor to a turbine.
 32. The system asin claim 31, further comprising: at least one preheater combustor, saidpreheater combustor receiving air directed from said air staging valveand being connectedly situated upstream from said catalyst module.
 33. Asystem as in claim 31, further comprising a cooling and dilution flowport for the transport of compressed air.
 34. A system as in claim 31,further comprising a turbine for the receipt of said effluent gasstream.
 35. A system as in claim 31, wherein said system is enclosed ina pressure casing.